A new SERL academic paper has just been published which compares actual metered energy use in 1,374 gas heated British households against Energy Performance Certificate (EPC) predicted use. The paper finds that while EPC A and B rated homes perform broadly as predicted, bands C-G use significantly less energy than the EPC model.
The research converted both the EPC prediction and the actual metered energy use – with data collected from homes participating in SERL’s observatory data set – to a ‘primary energy use intensity (PEUI)’ measurement which allowed direct comparison between smart meter data and EPC ratings for the first time. The gap between the EPC prediction and the actual energy used widens towards the F and G rated homes which used much less energy than EPC predictions in the homes in the study.
It is important to note that the research is observational and so is not able to explore what effect energy-efficiency upgrades and other factors would have on the EPC ratings of the homes in the study. So for example, some homes’ EPC ratings could be out of date, and could have had a more efficient boiler or insulation installed since the certificate was issued. It’s also important to note that EPCs are not expected to provide a highly detailed bespoke rating for each home.
It is encouraging to note however that it seems that lower EPC rated homes are not using as much energy as EPCs suggest, and that our general housing stock may be more efficient than EPCs imply.
The research also looked into a subset of homes which matched the EPC model’s assumptions around occupancy, thermostat setting and whole-home heating as it has previously been thought that this could account for a difference between the model and actual energy use. Our research suggests that occupant behaviour does not account for the discrepancy as the pattern of an increasing gap remains for this subset.
As EPCs are an important tool in measuring home energy performance and influence associated national policy, this research should lead to further investigation of the EPC model and process of assigning an EPC rating. This could have significant impact on energy policy as the country targets achieving net zero.
This research illustrates how the investment in the Smart Energy Research Lab to enable the gathering of real-world energy-use data is having a tangible effect on improving our understanding of the way is being energy used in the UK and supporting improvements in relevant policy.
Access the paper: ‘The over-prediction of energy use by EPCs in Great Britain: A comparison of EPC-modelled and metered primary energy use intensity’.